In the above technical field, patent literature 1 discloses a technique of searching for a person dressed in a color or pattern designated by query text of clothes from a video. Patent literature 2 discloses a technique of determining area security by comparing the feature of the color or pattern of the clothes of a person in a video with the feature of a color or pattern stored in advance. Non-patent literature 1 describes a technique of detecting a person position from a video based on a head, and extracting the features of the color and pattern of the upper half of a body model as a person feature.